Color television tube and process



Aug. 5, 1952 J. BRAMLEY 2,605,303

COLOR TELEVISION TUBE-AN'D PRQCESS Filed Feb. 17, 1951 2 SHEETS-SHEET 1CONDUCT/1V6 GRID A7 FIXED VOLTAGE C O/VDUC 7" //V6 LA YER VOLTAGE MODULATED INVENTOR A g- J. BRAMLEY v COLOR TELEVISION TUBE AND PROCESS FiledFeb. 17, 1951 GRID ELEMENT 0F 55c0-0 557' A7 D/FFERENI' .975"

F/XED VOLTAGE GAP/0 ELEMENT AT F/XED VOLTAGE PHOSPA/Ol? sir/P VOLT/1 6EMODULATED Patented Aug. 5, 195? UNITED STATES PATENT OFFICE 20 Claims.

The present invention relates to television, and particularly to colortelevision reception.

A purpose of the invention is to dispose semiconductor phosphor areassuitably of difierent colors in a particular geometric relationship in acolor television tube adjoining the face plate, and to produce an imageinstantaneously having a particular color by deflecting an electron beamso that it will illuminate only areas of the desired color at theparticular instant.

A further purpose is to obtain color television reception from a tubehaving the external appearance of a black-and-white television tube.

A further purpose is to enhance the brightness of the image on a colortelevision tube.

A further purpose is to shift an electron beam repeatedly for a seriesof short time intervals into contact with a plurality of geometricallyplaced semiconductor phosphor areas, the electron beam impinging uponphosphor of a particular color at a particular instant, and impinging onphosphor of another color at the next instant.

A further purpose is to place a plurality of strips or other areas ofsemiconductor phosphor of a given color on a conducting layer adjoiningthe inside of the face plate.

A further purpose is to utilize semiconductor phosphor areas, each ofwhich is a constituent of a multiplier element consisting of aconducting base, a thin layer of semiconductor phosphor dielectric andthen a secondary-electron-emitting layer.

A further purpose is to pass the electron beam to the semiconductorphosphor through openings, which are suitably slits, in a grid locatedbetween the electron gun and the conducting layer adjoining the faceplate, and to maintain a predetermined and selectively changing voltagerelationship between the grid and the conducting layer, the conductinglayer being preferably negative with respect to the grid and the gridbeing preferably at anode potential.

A further purpose is to shield the phosphor subjected to the electronbeam passing through one grid opening or slit from the electron beampassing through another grid opening or slit by a baffie extending fromthe grid toward the conducting layer.

A further purpose is to provide a baflle of dielectric having a depositof semiconductor on one or preferably both sides of the bafile.

A further purpose is to place the semiconductor phosphor of a particularcolor, preferably in the form of multiplier elements, on one side ofeach baflie.

A further purpose is to extend the phosphor areas as parallel stripsrunning lengthwise of the slits in the battle, and to locate the stripsof a particular color in the same geometrical relationship to each slitand in the path of the electron beam.

A further purpose is to project the electron beam diagonally withrespect to the major plane of the grid.

A further purpose is to deflect the electron beam diagonally withrespect to the major plane of the grid by electromagnetic or preferablyby electrostatic means and to vary the extent of deflectioninstantaneously to show images of different colors.

A further purpose is to carry the semiconducting layer on the baflieinto contact with the conducting layer on the face plate at, at least,some points.

A further purpose is to place the grid closer to the conducting layer onthe face plate at the side of the face plate remote from that from whichthe diagonal electron beam comes than at the other side.

A further purpose is to place the grid closer to the conducting layer atthe extremities than at the center.

A further purpose is to construct a color television cathode ray tubehaving an electron beam directed upon a, transparent plate adjacent toand across the face of the tube, to place a partially transparentconducting layer on the plate inside the tube, to mount a conductinggrid extending across the tube between the electron gun and the plateadjacent the conducting layer and having openings, suitably slits, whichpass the electron beam toward the plate, to provide semiconductorphosphor of a plurality of different colors arranged in different areas,suitably strips, in the path of the electron beam between the grid andthe conducting layer beyond the respective openings, in electricalcontact with the conducting layer, with the phosphor of a particularcolor in the path of the beam only at the same angular position beyondeach opening, and to arrang means for maintaining the grid at aparticular D. C. voltage and means for maintaining the conducting layerselectively at different D. C. voltages, at least all but one of whichare difierent from the voltage of the grid.

A further purpose is to produce color images on the face plate of acolor television cathode ray tube by introducing a transparentconducting layer across the tube inside of and adjacent the face plate,distributing semiconducting phosphor areas, preferably multiplierelements, over the tube adjacent and in electrical contact with theconducting layer in a geometrical pattern, suitably parallel strips,having a plurality of phosphor colors at each locality, projecting ascanning electron beam in the tube on phosphor of the same color in thedifferent localities, and deflecting the scanning beam at frequentintervals to impinge it on phosphor of another color in the differentlocalities.

A further purpose is to obtain electron multiplication in the electronmultiplier phosphor elements much higher than that obtained in priorpractice. This is accomplished in this invention by the properconstruction of the composite surfaces which make up the multiplierelements. One method is to interpose a semiconductor phosphor dielectricbetween a layer with at least moderately high secondary electronemission properties and a. conducting base. The semiconductor phosphorlayer plus the secondary-electron-emitting layer should have a thicknessof between 2 and microns.

A further purpose is to obtain high multiplication in asecondary-electron-emitter having a phosphor dielectric without theundesirable features of photo-electric effects due to the presence ofphoto-electric material, such as caesium, in the layer emittingsecondary electrons.

A further purpose is to maintain close time coordination between theexcitation of a phosphor and the primary current by providing forthe-neutralization by electrons of the positive charge in the phosphorlayer at a rate predetermined by the primary current. One method ofaccomplishing this is by depositing a secondaryelectron-emitting layeron an extremely thin layer of porous phosphor dielectric which itselfrests on a conducting base, and intruding particles of the secondaryelectron-emitting-layer into the pores of the phosphor dielectric toassist in neutralizing the positive charge by electrons.

A further purpose is to increase the efficiency of cathode ray tubes byemployingafine wire mesh with a surface having enhancedsecondaryelectron-emitting properties in a cathode ray tube in which ascreen, suitably double layer, is settled on a thin transparentconducting layer on the inside of the face plate. Aluminum constitutes asuitable choice for the conducting layer while the double layer mayconsist, for example, of ZnBeSiOi; Mn and ZnSzAg. The mesh may be at anegative potential with respect to the metal film on the face plate.

By proper choice of the emitting surface, the time lag between theprimary current and the secondary emission from the wire mesh can bemade comparable to the time between scanning frames. This is equivalentto a storage effect and will materially reduce the primary currentneeded to excite luminescence. Besides the screen materials mentionedabove, the following may be used as components of the screen: Anyorganic crystalline or vitreous phosphor, or crystals of alkali halidesimpregnated with rare earth, such as sodium chloride with europium oralkaline earth halides with rare earth elements in the solution such ascalcium fluoride with samarium.

The type of cathode ray tubes in which the screen comprises multiplelayers of phosphors which emit radiation of suitably chosen wave lengthcan be utilized to produce color images provided the variation inpotential difference between the mesh and the conducting layer on theface is synchronized with the color frame frequency of the total pictureframe transmitted. By proper choice of the potential, relative to thecathode, of the mesh and of the conducting layer on the face plate thepicture rasters of each color can be adjusted for perfect superposition.

The color will, to some extent, depend on the time lag and the currentdensity of the secondaries emitted by the mesh scanned by the primarybeam. Since phosphors vary in emission time and saturation of emittedradiation under uniform electron bombardment, the instantaneous color ofany point on the phosphor screen will be characterized by the timedistribution of the secondary electrons.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerousembodiments in which my invention may appear, selecting the forms shownfrom the standpoints of convenience in illustration, satisfactoryoperation, and clear demonstration of the principles involved.

Figure 1 is a side elevation, partly in central longitudinal section,showing a skew-neck tube to which the principles of the invention havebeen applied.

Figure 2 is a faceplate elevation of the tube of Figure 1.

Figure 3 is a fragmentary enlargement of Figure 1 showing the transversesection through the grid, bafiles, conducting layer, and face plate, inthe direction transverse to the length of the slits in the grid.

Figure 3 is a fragmentary enlarged plan view of the grid from the sideopposite to the face plate looking toward the face plate.

Figure 3 is a fragmentary variation of Figure 3*.

Figure 4 is an enlargement of a portion of Figure 3 showing the mannerof holding the baflies and showing the semi-conducting coating on thebaffles.

Figure 5 is an enlarged fragmentary variation of Figure 3 showingphosphor multiplier elements applied to the baiiles and to theconducting layer.

Figure 6 is an enlarged variation similar to Figure 3 showing phosphorstrips located entirely on the conducting layer.

Figure 7 is a fragmentary side elevation of a cathode ray televisiontube having electromagnetic modulation of the electron beam.

Figure 8 is a fragmentary diagrammatic side elevation, partly in centrallongitudinal section, showing a variant form of vacuum tube embodyingthe invention.

Figure 9 is a diagrammatic view similar to Figure 3 showing a differentform of grid construction.

Figure 10 is a diagrammatic perspective view illustrating asynchronizing device.

In the drawings like numerals refer to like parts throughout.

The present invention is applicable particularly to color television ofthe character which depends upon persistence of vision of the .observerto visualize a color picture when he in fact may see a rapidly changingsequence of pictures, each at an individual different color. Theindividual pictures -will desirably be of three difi'erent primarycolors, red, blue and green, shown to the observer in rapid succession.In the prior practice this result has been achieved by mechanicallymoving a filter, thus necessitating the employment of rather bulkymechanism adjoining the face plate. One of the important advantages ofthe present invention is that the color television image is produced bya cathode ray tube having an external appearance which is similar tothat of an ordinary television tube. The cathode ray tube of theinvention, however,

provides near the face plate a plurality of areas of phosphors each of adifi'erent color and arranged according to a geometrical pattern. Thephosphors desirably will emit red, blue and green light respectively. Bythe invention it is possible to excite the phosphors of different colorsone at a time and have each phosphor cease luminescence promptly. Theshift from one phosphor color to another can be accomplished in a matterof microseconds. Since phosphors have normally been insulators, animportant aspect of the invention is the employment of phosphors whichare semiconductors, either due to the composition of the phosphor itselfor due to the employment of multiplier elements which render thephosphors semiconductors. The shift of the excitation from one colorphosphor to another is desirably accomplished by maintaining thephosphors at suitable potentials and changing these potentials at veryshort intervals.

The present invention is a continuation-inpart of my copendingapplication Serial No. 612,197, filed August 23, 1945 forSecondary-Electron-Emitting Surfaces, now Patent No. 2,548,514, andcontains subject matter related to my U. S. Patent No. 2,527,981, issuedOctober 31, 1950.

The employment of the phosphors emitting light of different colors ascomponents of composite surfaces gives rise to enhanced secondaryelectron emission. The conductivity of the phosphors is suitablyadjusted to keep the charges from accumulation at the surfaces and it istherefore possible to keep bombarded surfaces of the phosphors at thepotential of the conducting base. It is desirable to correlate thethickness of the phosphor layer and the velocity of the bombardedelectrons to obtain maximum light output of the desired color.

The color television tube of the invention may desirably have theexternal appearance of the present skew-neck black-and-white cathode raytube except for an extra electrode which may be considered to be anextra anode (although it need not be at anode potential). The color ofthe picture presented on the face plate depends on the voltage appliedto this extra electrode. For example, changing the color of the picturefrom red to blue requires only a voltage change on the extra electrode.The potential of the first or standard anode is unchanged. Thus there isno over-all change in the deflection or focusing of the electron beam.

One great advantage of the invention is that it increases the brightnessof the image on the color television tube.

Referring to Figures 1 to 4 inclusive, in the preferred embodiment, thecathode ray color television tube has a face plate 2! provided with theusual television screen which is scanned at any suitable rate accordingto any scanning system involving for example 525 line elements, 405 lineelements or any other suitable number of line element as desired. Theelectron gun assembly 22 of any standard character is assembled in askew-neck which projects a diagonal electron beam on the inside of theface plate. A semitransparent conducting layer 23 (called transparentelsewhere in the specification) extends across the tube adjacent theinside of the.

face plate. No particular advantage exists in depositing this layer on aseparate .plateand therefore in most cases it is deposited on the insideof the face plate itself as shown.

The layer 23 is designated herein as a con ducting layer although itwill in most cases be a semiconductor, and may have the same compositionas the semiconductor layer later referred to. The conducting layer 23 isconnected by a separate insulated terminal 24 which is led out throughthe glass or other wall material of the envelope of the vacuum tube andis insulated from all other terminals.

The technique of providing transparent conducting layers on glass asnormally used for the face plate is well known. This is described inLeverenz, Luminescence of Solids (1950) 471, which refers to PittsburghPlate Glass Company Technical Glass Bulletin No. 15 on Nesa CoatedGlass, Corning Glass Works Bulletin on E. H. Coated Glass and J. W.Littleton U. S. Patent 2,118,795, granted May 24, 1938. Commontechniques for depositing transparent conducting coatings on glass arethe evaporation of aluminum in vacuum, and the deposition of tin bydecomposing tin chloride. Any other well known method may be used asrequired.

Semiconductor phosphor of different colors is placed in different areasadjacent the conducting coating and in the preferred embodiment isdirectly placed on it as shown in Figure 3. In any case the phosphorshould be in electrical connection with the conducting layer 23.

The semiconductor phosphor may be produced in one of two manners (1) Itmay be a single layer of phosphor containing impurity centers andprocessed to create a semiconductor as later explained; or (2) It may bea multiplier element as later explained. As best seen in Figure 3,semiconductor phosphor areas 25 and 26 are shown on the conducting layer23, located successively in a sequence in which the areas bear the samegeometrical relation to one another, all of the areas 25 having phosphorof one color and all of the areas 26 having phosphors which luminesce inanother color. In the form shown the phosphor areas are parallellongitudinal strips, but it will be understood that they may take anysuitable form in which the phosphor of one color can be selectivelyenergized by the electron beam. The character of the phosphor itselfwill be discussed at a later stage in the application.

The individual colors assigned to the phosphor areas 25 and 26 will be amatter of choice; for example 25 may luminesce green and phosphor 26 mayluminesce blue. Since in the preferred embodiment different voltageswill be applied to energize difierent phosphors, the green luminescingphosphor will desirably have a thickness corresponding, for example, toa maximum light output at 5.4 kv. bombarding electron-voltage, while theblue luminescing phosphor will have a thickness corresponding to thatwhich gives maximum light output at say 6.2 kv. bombarding electronvoltage, the thickness relations being well known in the art.

Placed across the tube between the electron gun 22 and the conductinglayer 23 is a grid 21 suitably of metallic wire or sheet. A satisfactorymaterial for the grid is aluminum, nickel or stainless steel or any ofthe structural alloys. In the preferred embodiment as best seen inFigures 3 and 3, the grid 21 consists of a stamp.-

7, ing having-longitudinally extending metallic strips 28sspaced bylongitudinally extending slits Inrthe preferred. embodiment the slitswill extend-uninterruptedl'y from one side to the other of the-grid,having merely cross connection-at theends so asnot to create theshadowon: the-screen incident to cross connection at intermediatepoints'.'Thegrid'is located close to the conductive layer, the distance betweenthegridL-andthe' conductive layer being desirably of the order of 2There-should be one grid slit .for everyrline on the screen, and thelateral distance from the center of one slit to the center of the nextslit may desirablybe of the order of 1 mm. Theslits'on the grid runperpendicular to the line in-thescanning of the screen. Thestructurewhich :is being shown for a few grid slits will be repeated foreach one of the line elements of the grid system.

The grid has an external terminal 3| which is insulated from all otherterminals and led out through the glass or other envelope of the tube.

Itwill: be obvious fromFigure 3 that each of thephosphor-strips 25 and26 extends parallel tothegridslit, and is oflset-with respect to thegrid slit away from the direction from which the electron beam: entersdiagonally so that the phosphor :strips will be within or close to thepathof the electron beam depending on the voltages.

An anode-coating 32 is placed on the inside wall of the tube from -apoint near the forward end of the. electron gun to a point rearward ofthe grid and this coating 32, suitably of graphite (Aquadag) isconnected to terminal 33 which is insulated from all other terminals andextends through the envelope of the tube. Anode coatings of thischaracter are well known.

In order to confinethe electron beam passing through each slit to thephosphor corresponding to that line element, and also in order tosupport'an additional set of phosphor strips in the preferredembodiment, baiiles 34 extend from the grid toward the conducting layerand at an angle suitably approximating the angle of the diagonalelectron beam. Where the electron beam approaches the grid at 45degrees, the angle between the bafiies and the major plane in the gridwill desirably be made about 42 so as to allow adequate space for beamdeflection to encounter the'proper phosphor.

The baille is suitably made of an insulator such as mica or glass, andin the preferred form where phosphor is placed on the baflle, the bafileis coated on oneor preferably both sides by a semiconductor layer 35which extends suitably the full length of the baiiie. The semiconductorlayer 35 may consist of a layer of aluminum or tin or any other suitablemetal as explained in connection with the composition of conductinglayer 23. In fact it may be the same as conducting layer 23 except thatit must have a resistance of at least one megohm per baiile, while nosuch limit is necessary on the conducting layer. This limit is imposedon the semiconducting layer to avoid short circuiting the grid to theconducting layer.

The baflles desirably extend far enough so that at least in places thesemiconducting layer 35 on the 'baiile touches the conducting layer 23at the face plate at forward ends 36. This allows a progressive voltagedrop to occur from the grid to the conducting layer.

The :manner of mounting the haflle on the grid is not critical in thepresent invention, the form shown involving thecreati'on of reversebends-'31 running across the grid which are angular-1y dis posedinthedirection to be taken by the-baffle,

and which receive and grip the end ofthemaifle and electrically connectits semiconductinglayers- 35 to the grid.

At the side of the baflie remote from the side at which the diagonalelectron beam enters,' and extending along the full length of the bafllewhich corresponds with the full length of the -grid-slits and the fulllength of the screen, I place semiconductor phosphor areas, suitablystrips 38, which luminesce in a difierent color from' the phosphor onthe conducting layer 23. As shown, the strips 38 extend along near theends of the baiiles adjoining the conducting coating-.23. If the strips25 luminesce green and thestrips 26 luminesce blue, the strips 38 willluminesce red to provide the other desired primary color. An importantaspect is that the strips 25 andv 26'are spaced by a distanceapproximately equal to the width of the strips, and the phosphor strips38- are placed immediately behind the spaces 40 between the phosphorstrips 25 and 26 so that the luminescence of the phosphor strips 38'willbe seen at the front of the face plate through the gaps All between thephosphor strips 25 and 26.

In a suitable embodiment, the apertures -'between the metallic gridstrips may be of the order of 0.30 mm. while the widths 'of the strips-25 and 26 of phosphor and the spaces between them may suitably be of theorder of 0.25 mm- The width of the phosphor strips 38 may convenientlybe the same or somewhat wider in view of' t'he angularity.

It will be evident that the separation between the grid and theconducting layer on the face plate should be suficient to maintain thenecessary voltage between them without arcing, and of course thesemi-conductor layers 35 should have a high enough resistance so as notto interfere with adequate insulation of the grid from the conductingcoating at the face plate.

The red luminescing phosphor 38 is suitably of a thickness which willgive a maximum light output at a bombarding electron voltage ofapproximately one-half the anode voltage.

The electron beam in the cathode ray television tube is deflected so asto encounter one color of phosphor at a time, and the picture in thatcolor is broadcast at the same instant so that this particular color ofphosphor is energized. In the form of Figures 1 to 4, the deflection ofthe electron beam is accomplished electrostatically. The grid '21 willdesirably, although not necessarily, be at anode potential, and whateverits potential it will be maintained at a constant D. C. potential. Theconducting layer 23 on the other hand will vary its potential dependingupon the color of image which is being produced by the tube. The voltageof the conducting layer may be either negative or positive with respectto the grid, but it is decidedly preferable to make'it negative, as thisgives a much more powerful beam deflection than would be the case if itwere positive with respect to the grid. All the grid elements in thisform are at the same potential. The normal procedure therefore would beto maintain the conductive layer 23 at a particular voltage negative tothe grid (or possibly at the same voltage as the grid) to energize thephosphor 26, to make the conducting layer 28' to energize the phosphor38. As you 'make'the conducting layer more negative with respect to thegrid, you deflect the electron beam farther away from its originaldiagonal axis.

Thus to obtain a picture in the one color, say blue, the conductinglayer might preferably be connected to a voltage slightly negative withrespect to the grid and will energize the blue phosphor 26 at each lineelement; After the beam has scanned the face plate to'form a picture inblue, the potential of' the conducting layer is shifted to a value morenegative with respect to the grid, shifting the electron beam'to impingeon the phosphor areas 25 and energizing'the green phosphor. When thisshift in beam deflection occurs, the blue phosphor 26 immediately ceasesto be luminescent, due to the elimination of time lag by thesemiconductor action of the phosphor already described, whileluminescence of the green phosphor begins immediately. The beam thenscans the screen and creates a green picture. The conducting layer 23 isthen made still more negative with respective to the grid and theelectron beam past each slit shifts to encounter the red phospher 38. Atthe same time; due to the absence of time lag in the semiconductorphosphor, the green phosphor 25 immediately ceases to luminesce. Theluminescence of the red phospher 38 shows through the gaps between theblue and the green phosphor.

Of course the color of the phosphor applied at the different places maybe shifted around as desired, and the red, blue or green phosphors maybe at any of the areas 25, 2B or 38 as preferred.

It is highly desirable to use a skew-neck tube which will give anormally diagonal relationship of the electron beam to the major planeof the grid. This makes the deflection much more sensitive to changes inpotential of the conducting layer 23 relative to the potential of thegrid.

It is preferred in the skew-neck tube to make the grid curve as shown inFigure l and to place the grid closer to the coating 23 at the side 4|opposite to that from which the diagonal beam is directed and fartheraway at the side 42 adjoining that from which the electron beam isdirected. This corrects for the remoteness of the electron beam sourceat the side 41.

The curvature of the face plate 2| (it is normally a portion of thesurface of a sphere) can if desired be predetermined in relation to theangle of skew of the electron gun so that the electron beam will passthrough all slits in the grid 2'! at the same angle, in which case thegrid 21 will have the same curvature as the face plate and willeverywhere he at the same distance from the face plate. Where, however,it is not desired to employ this condition of uniform spacing of thegrid with respect to the face plate, the tube designer may employ theoption of spacing the grid farther from the face plate the steeper theangle of incidence of the electron beam on the grid. This in effectcalls for a variation in steepness in the angle of the electron beam onthe different slits of the grid so that the beam will encounter phosphorstrips at the same geometrical position for the same potentialdifference be tween the grid and the conducting layer at all lineelements across the grid. If the angle of incidence of the electron beamvaries over the grid and it is not desired to fully correct for this byvariation in the spacing of the grid from the conductinglayer,-correction can be made by varying the spacing of the phosphorstrip with re- I0 spect to the normal from the center of the grid slitwithin limits.

In the illustrations in the drawings the slits 30 of the grid have beenshown to be horizontal. In this case the scanning will normally follow-aseries of vertical lines. It .will be understood however that theslitsin the grid may if desired be 'vertical in whichcase the scanningshould preferably be horizontal. While there are advantages in bothvertical and horizontal scanning, I prefer to employ horizontal scanning(with vertical grid slits). The reason that this last embodiment ispreferable arises from 'the fact that the electron beam as well knowninthe art must change its focus as it travels from one end of the rasterto the' other because the distance between the gun and the point ofimpingement of the electron beam on the phosphor varies from point topoint on the face plate. as you move up vertically.

The exact voltages used in modulating the conducting coating for colorwill vary, but the following is a suitable example: The anode potentialand the potential of the grid 21 is 10 kv. The conducting layer-23 isset'at 6 kv., for blue light (phosphor 26) 5.5 kv. for green light(phosphor 25) and 5 kv. for red light (phosphor 38). During each settingof the voltage of the conducting layer 23, the grid of the electron gunis modulated to scan the picture for that color image.

The radiation produced under any particular phosphor color doesnot ofcourse need to be percent pure. Thus in green the light produced may be8 percent blue, 8 percent red and 86 percent green, while in blue thecolor produced maybe 12 percent red, 6 percent green and 82 percentblue, but in either case this color purity is acceptable.

It will be seen that this type of three-color cathode ray tube isparticularly well adapted to the C. B. S. or C. T. I. systems of colorbroadcasting. There are two special advantages over the mechanicallyoperated color filter now recommended for C. B. S. reception:

1. The three-color cathode ray television tube can be made in the samesizes as the conventional cathode ray tubes, while tubes having adiameter over 12 inches are not practical in the mechanical system usingrotating filters.

2. The brightness of the picture is greatly increased. The brightness ofthe picture obtained with the C. B. S. mechanical color filter isreduced to one-seventh that obtained from the standard black-and-whitecathode ray tube, with the same power input to the scanning beam. On theother hand, the brightness of the picture obtained from the three-colorcathode ray tube of the present invention is approximately one-thirdthat obtained with the standard blackand-white cathode ray tube, usingthe same power input in the scanning beam. This means that a colorpicture can be readily obtained with a brightness to which the public isnot accustomed in present day color television reception.

Figure 3b shows a grid 21 having a series of short slits 30' in line,which may less desirably be used instead of the long slits 30.

The form of Figures 1 to4 can be still further improved in the bestembodiment by using multiplier elements at the phosphor areas. Thesemultiplier elements will comprise a conducting base, which in this caseis the conducting layer 23 or the semiconducting layer 35 as the casemay be, covered by a thin layer of semiconductlng; phosphor dielectric43.- described' below and superimposed by secondary electrons-emittinglayer;

The; light :emitted'ishowsthrough .the' extremelythinlsecondary-electron -emitting layer: 44 in 1311850359 ofthe-phosphor strips amounted on thesemieconducting layers 35; It.-willbe understood-without repeating-the illustrations that in each-:case in.which a phosphor layer isshown, there will preferably he a.- multiplierelement consisting.ofconductingbase; then a semiconducting phosphordielectric; layer and then a: secondary-electron-emitting-rlayer on theopposite side: of the dielectric layer. The -.multiplier ele:-ment--more-reliably neutralizes .thecharge on the phosphor and:assures.- absence of time lag;

In: somecases-i it isdesirabletoplace all: of theaphosphor stripson'ztheiconducting layer: 23 instead: of placing one:- .set: on the.bafiiesi In Figure 6 I show strips 38,: which: maysuitablybeethesreiphosphor positioned beside the strips 25.;and:26::withsuitable spacing-40 between to avoidiunintentional, energizingby overlapping; of the-areas energized by the beam. Thesesistrips255.26zand ,38' will desirably eachtie-multiplier elements. Thebafiiess-are optionallyi omittedrin Figure 6. They may: bezused 'ifdesired .to re-v duce scatteringror-serve aszsupports;

While in -n1ost cases .it ;is :preferable :to. use-.an electrostatic;:beam: deflection; system, the. beam can be deflected in additionelectromagnetically ascshown' in Figure; '7. 'Ihisccreates an :acuteangle between: the entered: beam and :thegrid 21:1 'I'he grid,.FigureZymay. be of theziorm already describedcin-Figuresl'toad;. The usualCOIIVBI'? gencezcoil 45 is provided. (if the focusing .is-.electromagnetic; and .otherwise the. focus will beaccomplishedzin thegun structure) :and; the usual anastigmatic deflection yoke; 46 is:employed; mcoilfl forlinear deflection surrounds the gun awayvfrom thefaceplate withrespect to the -convergenceicoil 45.andthis deflectstheelectron beamangularlyin much the same-way which the skew-tneckitubedeflects zit angularly. Thedeflec tion coil 41 is energized fromasuitable alternating current: source. In the electro-magnetic formof-ideflection, if the curvature of .the face plate and gridare not setto give the same angular relationshipzat:.all points on: thezgrid, thenthe grid is placeds-closer to the faceplate at 481near the extremitiesthan at 49'near the center of the face plate-to correct -for thedifierence in angle--of the electron beamat thestwo points. Bafilesifusedshould slope one way on one side .of the cen terrandithe othervway-v on the other side. of the center.

Andmportant aspect of the invention relates .to the production ofelectron-tubesof highemission ofisecondary electronsas a consequence ofstrong electrostaticfields initiated by 'bombardmentwithprimary-electrons of composite surfaces.- constructedlin-accordancewith-the invention. There must-of;:course-sbe--a-; suitable, source ofprimary electrons and these electrons: should have .aspeed such, that"the-ratio of the :secondary electrons released from thesecondary-electron-emitting elementto the primary-electrons of thebeam:impinging on the secondary electron emitting element; is greater thanunity such velocity furthermore-beingsuchthatinacathode ray tube thetime .lag-;between impact of the electrons -in-the scanning, .-beam .andthe emission of secondary electronsless thanthe time of persistence ofvision., There .must be a perforated surface between:;the;.-.primarysource and thephosphor. di-.

12 electriczof thezseconda lemittingsurfacerrwhichperforatedsurfaceswill allow-the-beam notconly to go through: it;butinrits travel in-the scanning path-to find aeperforated .surfacefatallzpoints through which. it: can;pass.- Theinventionmay-beusefullyz-appliedtin image converterorcathoderayctubes-orlight-waivesto.:intensiy the. images produced by-electromime pactonfiuorescentor-zlight valvascreensz- While the example-,igivenzbelow hasfbeerrdirected par ticularlyz-toicathode ray; tubes, eit'WillzbE?evident to those skilled in;the art that it 'c'anzbeiappliedequallyzwellg-tozimage convertors andlig'ht valves:

Eon" cathode: ray; tubes; the; conducting layer on the inside oftheziacelplatezshotrldrbemapabl of transmitting at-least %:ofltherlightimpin ed upon ;it:- It-is desirable: tomave-iameanseofiade justing the:conductingjlayen to; az-zdeflniterpo tential. For-:example-ain Figure-8lthez-film-l 50 on the-interior surface of the. face.:-plate.:ofid:hecathode;- ray: tube: is: connected; to terminal; 511 Layer-25 1s;a.:phosphor:-lay.er:orrlayers ofrzdifirent phosphorsssettlednoreotherwise deposited onthe conducting layer "58 Therlayer :50 may: beofthe same character. 25213116 conductingzlayeian already described.The; potential of? the grid is maintained. at the value of "theianodetpotential by connecting the- :grid. .52;':to' the colloidalgraphite coating 32 on cthez;inside of theetubev Thea-grid shouldbezcoated'andpreparedto :produceanuenhanced-rsecondary; electronemissionw Thef very high secondaryeelectronz emissiomleads towcoriresponding. increases the efiiciency light emission as measured in termsof lumense'per watt of electrical. energ-y inputrbyproperadjustment ofthe conductivity. of .the=.dielectric in-the compositev surfaceemittingasecondary, electrons. The bombardmentv ofthescreenbycthesecondary e16Ct1OnS .C8-l1 be extended. ovenar-sizablefraction of the frame-period of-sthe ,scanningsbeanr. Thisisequiizalenttoastorage efiect...

Figure 8 showsa cathode ray tube, .inL which, however, theconventionaLelectrongun and the electrode .system. for. accelerating,focusing and deflectingtheelectrons have been omitted from the drawing.

In the previous .description the. grid 21Ihasiin all cases beenmaintained at the same voltage throughout. The invention can also beappliedin a form using a grid having alternate elements of differentpotentials. Figure 9 illustrates. grid wires 53 at anode potential whichextend in parallel relationship with. respectto grid.'wires 54 which areelectrically negative with respect tolthe wires 53. The grid ispositioned between the eleca tron gun and the conducting layer 23'as.'in Figures l to 4 inclusive. Grid wires 53 andf54 are insulatedfrom one another. The respective D. C. voltages of the grid wires 53 and54 do not change during, the operation. The conducting coating 23 ismaintained at diflerent voltages as'in the form of Figures 1 to 4 todeflect the electron beam. Bafiles 34 "suitably provided withasemiconduct ing layer 35 on one or preferably both sides are carried onone side of each wire 53,"attached'-in any suitable way as by adhesive.The'bafiles' are desirably :disposed 'at an angle-to thenormaksufficientrto provide for the proper'angle ofxiflec= tion of :theelectronbeam; suitably'15 degrees; In this 'case, simplyas-anillustration that any suitableselection of colors may be made, one'setof phosphor strips-25 is provided-onthe conductive layer '23, although asecond set as-in 'Figure 3 may-be used if desired. Aset of phosphorstrips 38 is provided on: the. semiconductinglayer 35 on 13 the side ofthe baffle which may be bombarded by electrons deflected by the positiveand negative wires of the grid system which form part of the deflectionsystem.

In this construction only alternate grid slits or apertures are useful.When the coating on the face plate becomes more negative with respect tothe anode potential, the beam is shifted toward the bafiie on thepositive grid element.

The manner of changing the voltage applied to the conducting layer tocoordinate with the broadcasting will vary with the particularinstallation, the simplest procedure being to use the well known systemby which a synchronous motor operates the C. B. S. rotating color discin step with the broadcast to bring the proper color filter into properposition at the correct time. I illustrate this diagrammatically inFigure where a synchronous motor 55 turns a shaft 56 in synchronism withthe broadcasting, turning a contact block 5'! having respective contacts58, E8 and 6! at different positions, which receive voltages proper forthe three voltage settings of conducting layer 23 through slip rings'62, 63 and 64 connected to the respective contacts 58, 60 and El andinsulated from the other contacts. A brush 55 rides the contacts 58, E9and GI and successively applies the difierent voltages to the connection24 of the conducting layer 23. Thus the picture impulse and scanningoperations are performed three times, once for each color, insynchronism with the sending station, for each picture.

Phosphor composition The phosphor forms what is termed by Leverenz,Introduction to Luminescence of Solids (1950) p. 452 and 453, a linestructure screen. The phosphor need not in all cases be a multiplierelement consisting of separate layers, but may in some cases be a singlelayer converted into a semiconductor by proper treatment as laterexplained. Any suitable phosphor may be used either for the single layeror multiplier element phosphor. examples being given by Leverenz atpages 452 and 453. Thus the blue phosphor may desirably be the blueemitting hexagonal ZnSzAg, while the green emitting phosphor may begreen emitting rhombohedral ZnzSiOuMn and the red may be red emitting(ldzBz-oszMn (the element following the colon is the activator as in theusual nomenclature). The preparation of the zinc sulphide and cadmiumsulphide for phosphors is described by Leverenz in Appendix I. Any oneof the phosphors may be made from zinc sulphide and cadmium sulphide byvarying the proportions to give the different colors as explained inLeverenz and shown by the curves on page 196.

Where a single layer is to be employed as the phosphor element withoutmaking a multiplier element, the phosphor may be converted into asemiconductor in one of several ways:

1. First have an excess of the metal above the stoichiometricproportions in a metallic compound. Zinc oxide prepared by burning zincin insufficient oxygen to obtain complete oxidation is an example ofsuch a semiconductor phosphor.

2. Another method is to replace one of the atoms in the phosphor crystalby another atom which is isomorphous, comes within the Hume RotheryVolume relation (about excess atomic size), and has a valence one higherthan the atom which it replaces. This free electron then becomes aconducting electron in the crystal. An example of this type ofsemiconductor is zinc silicate, ZnzSiO4:Mn to which a small percentageof impurity is introduced during the heat treatment. The procedure is toheat zinc silicate with a small percentage of manganese activator at atemperature of 900 to 1000 C. in an atmosphere of methane for about 15minutes. This intro duces impurities into the lattice. The sameprocedure can be used with other phosphors. Zinc sulphide with a smallpercentage of silver activator is heated in an atmosphere of methane at700 to 856 C. for about '60 minutes. ductor is formed.

The various other phosphors may be converted into semiconductors byusing any suitable method A semicon- 'as above described, and in suchcase the phosphors are suitable for use as semiconductor phosphor layersin the present invention without employing multiplier elements. In mostcases, however, it is preferable to obtain the semiconducting propertiesby using the phosphor as the dielectric of a multiplier element.

The method of applying the phosphor layer may be as pointed out inLeverenz, pages 381 and 382. Wet spraying and settling are suitablemethods. The techniques of applying phosphor discussed in C. H. Bachman,Techniques in Experimental Electronics (Wiley 1948) pp. 198 to 207 maybe used. Phosphor may be applied by evaporization using the techniqueemployed in evaporating metals from tantalum boats. The evaporation maybe carried out according to the technique of Bachman, pages 120 to 125.

Multiplier elements Many phosphors are likely to load up with electronsand cease to emit light because no beam electrons can strike them, sincethey repel the beam electrons. It is very desirable, therefore, that thephosphor should be part of a multiplier element which will dischargeelectrons into the tube and permit beam electrons to collide with thephosphor and produce continued luminescence. Accordingly it is verydesirable to employ multiplier elements as the phosphor strips or areas,rather than to rely on semiconductor phosphor as a single layer.

The multiplier element consists of a conducting base, a thin layer ofphosphor dielectric and a secondary electron emitting layer. It is ineffect a sandwich with the phosphor dielectric between the base and thesecondary electron emitter.

Where, as in Figure 5, the phosphor strips are applied on the conductinglayer 23, this layer functions as the conducting base of thesemultiplier elements. In the case of the phosphor strip applied to thebafile, the semiconducting layer 35 on the bafiie makes the conductingbase for the multiplier element on the bailie.

The base of the multiplier element is covered by an extremely thin layer43 of phosphor dielec trio. Any one of the phosphors referred to abovemay be used as the dielectric. In this case they will be treated to makethem semiconductors as part of the treatment of the multiplier element,and they need not be separately treated.

On the dielectric is deposited a thin layer 44 of a substance which is agood emitter of secondary electrons such as beryllium; beryllium oxide,IBeO; alloys of beryllium, particularly alloys of beryllium and copper;magnesium oxide; oxidized magnesium alloys; aluminum; alloyspredominantly consisting of aluminum such as duralumin of any of therecognized varieties, especially aluminum alloys 173 (Al Cu 4%,

Mgi.0.5%,;-Mn:0.5%) or aluminum alloy 245 ,(A1 93.8%,. Cu -.i: Mg 1.51%,Mn 0.5% orcthe aluminumI-magneSium (1,0%';or-30%) alloy, or. the.aluminum beryllium alloys, of which the one containing 30 beryllium:appears the most eflicient. Among :the above the aluminum alloys areunexpectedly efl'ective out-f allproportions-to any characteristicspreviously, suspected and greatly exceedmure aluminum in multiplication.

Thedayer '44 -is sufiiciently discontinuous to be partially transparentso that light from the phosphor can be emitted through it andelectronsfrom the gun can pass through it to excite thephosphor. Whenthis top ,secondary-electron-emittinglayer 44 is struck by;primaryelectrons under suitable. potential conditions it emits a largenumber-ofsecondary:electrons; and thus becomes positively charged-andcreates a strong. electrostatic fieldcbetween the conducting base andthe dielectriclayer-43. Thiselectrostatic field pulls out electrons fromthe conducting .base throughxthe dielectric, thus producing-highmultiplication of electrons.

The combined thickness of the dielectric layer andy-of the layeremitting secondary electrons mustbe very small, the desired range beinghetween-.2 and 20 microns. While :not in every .casemssentiaL-this range"of thickness should-be use'clziorbest results.

One of the problems in the-prior art has been to causerthesecondary-electronv emission to start and stop either incoincidence-with the primary current or after only a brief andcontrollable time interval. Malter (Marconi) British Patent 481,170,issued September 7, '1936, uses caesium andis' troubled'by time lagbetween-.the-starting of-the primarycurrentand the starting. of thehighsecondary-electrcn emission, as "well as between stopping ofrtheprimary current and the stopping of the secondary electron emission.'(Malter, Physical Review, vol. 49, page 478and page' 879 (1936).)Furthermore, caesium deteriorates by volatilization in vacuo and causesobjectionable photoelectric effects which prohibit the use of the layeras an emitting surface in-a photomultiplier tube. In the presentinvention the electron emitting layer is non-photoelectric, and manyadvantages and avoidance of-much difficulty are thereby obtained.

In order to prevent excessive time lag, the positive charge in thesecondary-electron-emit ting layer must be neutralized by electrons fromthe dielectric layer very quickly, but not quickly enough'to interferewith extraction-of secondary electrons by the electrostatic field; Theextraction time hasbeen estimated as about '10-' seconds.

The phosphor dielectric layer may-be deposited by spraying, settling,evaporation or similar methods as already discussed in connection withthe depositing of the phosphor layer when it is the'only layer on top ofthe conducting layer. The secondary-electron-emitting layer can bedeposited .on' the dielectric by dusting, evaporatiornsettling or thelike.

I have discovered that in order to produce the high field necessary forelectron extraction from the metallic base under the conditions of coldemission (about a million volts per centimeter), the thickness of thedielectric layer is ofimportance. A- voltage due to secondary electronemission of more than a few thousand volts is not obtained in practice.The-thickness should preferably not exceed 0.03 millimeter, and in anycase the thickness of the layer should notexceed 1.6 0.1 millimeter. No.limiton-thinness is necessary provided the dielectric functions.

The invention-is operative in its broader phases provided the metallicbase, phosphor dielectric layer and secondary-electron-emitting layerare as described, without further precautions to avoid time lag, but forbest results, special precautions should be taken-to assure that thephosphor is' a semiconductor and thus avoid time lag. There areseveral-ways of overcoming this trouble which have been discovered byme.

One method of overcoming time lag isto deposit the dielectric layerdeliberately with considerable porosity. This can be-done ifthe-dielectric is applied by the established technique of settling froma liquid, controlling the fineness of grinding of the particles.Particles with a diameter of the order of ten microns have been found-tobe satisfactory in obtaining porosity. If difliculty is encounteredwithcolloidal. properties an electrolyte may be added to cause .dispersionand hence-aid settling.

A suspensionis made of a semiconductor phosphor in a suitable liquid,for example water. The electrolyte frequently added is lithium.hydroxide or barium acetate in the proportion of a fraction ofa-percent. Thesuspension of phosphor settles. slowly upon the surfacewhich is to be coated, after which the supernatant liquid is drained oilbytilting orsyphoning and the coating is allowed to dry.

The-same effect may be obtained'by spraying the phosphor on the surfacein a suitable medium, for example cellulose nitrate lacquer. The porousphosphor layer is then coated with secondary electron emitter, using anydesired technique, after which the multiplier element suitably. in thetube is heat treated in a vacuum at a temperature from 500 C. up to thesoftening point of the glass and other components, for a time of atleast an hour at the lower temperature, diminishing with increase intemperature. This heat treatment enables molecules of the secondaryelectron emitting layer to penetrate the phosphor dielectric, thusassisting in preventing time lag by conducting electrons to the surfaceand neutralizing the charge.

As explained above, the field intensity which produces cold emissionwill fall too low if any individual dielectric layer is allowed tobecome thicker thanabout 0.1 mm., preferably 0.03 mm. If for any otherreason the dielectric layer must be thicker, this can be accomplished byseveral alternate layers of a phosphor dielectric and secondary electronemitter, each dielectric layer of optimum thickness and not exceeding0.1 mm.

Where the secondary electron emitter is beryllium it has beensuccessfully applied to the tube element by evaporation in vacuo byelectrically heated tantalum spires which serve as supports and heaters.It does not matter whether the beryllium is oxidized or not, since themetal and oxide are equally good as secondary electron emitters.

Where magnesium .is used as a secondary electron emitter the oxidationis essential, as the unoxidized magnesium is not a good emitter. Themetal will, however, oxidize readily in air. The effectiveness of.magnesium (oxidized) as a secondary electron emitter is greatlyimproved by the step of baking in vacuo at a temperature of 600 to 800C.

The secondary-electron-emitting layer should be free from poisoningingredients such as metallic nickel or less importantly cobalt.

It will be evident that by the invention it is possible to scanslightly'difierent line elements at intervals separated by a few microseconds and energize phosphors of different colors. The elimination ofthe difiiculty due to time lag thus makes it practical to obtain colortelevision re ception in a manner similar to the C. B. S. or C. T." I.systems without the difficulties incident to a mechanical color filter.

It will further be evident that by the invention improved brightness inthe color television images is produced to make it more nearlycomparable to the brightness of black-and-white reception.

When reference is made herewith to a D. C. voltage which is maintainedon the conducting layer for the purpose of deflection of the electronbeam, it will be understood that the voltage need be efiectivelyconstant only for a time of the order of a microsecond before it changesto another momentarily constant value.

In view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the process and apparatus shown, and I,therefore. claim all such insofar as they fall within the reasonablespirit and scope of my claims.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof the tube, a transparent conducting layer across the inside of thetube on the plate, a conducting grid extending across the tube betweenthe electron gun and the conducting layer adjacent the conducting layerand having slits parallel to one another which pass the electron beamtoward the conducting layer, insulating baflies extending along one sideof individual slits from the grid and in at least some places touchingthe conducting layer, a semi-conducting layer on one side of eachbafiie, semi-conducting phosphors of a plurality of diiferent colorsarranged in strips parallel to the slits selectively in the path of theelectron beam on the conducting layer with the phosphors of a particularcolor in the same geometrical relationship to each slit, semi-conductingphosphor of a different color arranged in strips along thesemi-conducting layer on each bathe in the same geometrical relationshipto each slit, the phosphors of the different colors being selectively inthe path of the electron beam through the slits, and means fordeflecting the electron beam into difierent angular relationships toenergize phosphors of different colors.

2. In a color television cathode ray tube having an electron gundirecting an electron beam upon a face plate, a transparent conductinglayer on the inside of the face plate, a conducting grid extendingacross the tube between the electron gun and the conducting layer,adjacent the conducting layer, and having openings which pass theelectron beam toward the conducting layer, a plurality of semiconductingphosphor areas engaging the conducting layer on the opposite side fromthe side of the conducting layer engaging the face plate, with phosphorof a plurality of diiferent colors arranged in different areas in thepath of the electron beam between the grid and the conducting layerbeyond the respective openings, with phosphor of a particular colorselectively in the path of the electron beam only at the same deflectionof the electron beam, means for maintaining the grid at a particularsetting of D. C. voltage and means for maintaining the conducting layerat diiferent D. C. voltages at least all but one of which are difierentfrom the voltage of the grid.

3. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof the tube, a transparent conducting layer across the inside of thetube on the plate, a conducting grid extending across the tube betweenthe electron gun and the conducting layer, adjacent the conductinglayer, and having openings which pass the electron beam toward theconducting layer, baffles at one side of the grid openings extendingtoward the conducting layer and. limiting deflection of the electronbeam passing through the openings, semi-conducting phosphors of aplurality of different colors arranged in different areas in the path ofthe electron beam beyond the respective grid openings between the gridand the conducting layer in electrical contact with the conductinglayer, with the phosphor of a particular color selectively in the pathof the beam only at the same deflection, means for maintaining the gridat a particular setting of D. C. voltage and means for maintaining theconducting layer selectively at different D. C. voltages at least allbut one of which are different from the voltage of the grid.

4. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof the tube, a transparent conducting layer across the inside of thetube on the plate, a conducting grid extending across the tube betweenthe electron gun and the conducting layer adjacent the conducting layerand having openings which pass the electron beam toward the conductinglayer, electrically insulating bafiles extending from the grid at theside of individual openings toward the conducting layer, asemiconducting layer on one side of each baflle, semiconductingphosphors of a plurality of difierent colors arranged in different areasselectively in the path of the electron beam between the grid and theconducting layer beyond the respective openings distributed on and inelectrical contact with the conducting layer with a phosphor of a.particular color in the path of the beam only at the same deflection,semiconducting phosphor of a difierent color on the semiconducting layeron each baffle, means for maintaining the grid at a particular settingof D. C. voltage and means for maintaining the conducting layerselectively at different D. C. voltages, at least all but one of whichare different from the voltage of the grid.

5. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof the tube, a transparent conducting layer across the inside of thetube on the plate, a conducting grid extending across the tube betweenthe electron gun and the conducting layer adjacent the conducting layerand having openings which pass the electron beam toward the conductinglayer, semiconductor phosphor of a plurality of different colorsarranged in different areas in the path of the electron beam between thegrid and the conducting layer beyond the respective openings inelectrical contact with the conducting layer, with the phosphor of aparticular color selectively in the path of the beam only at the same 19deflection, means for hi'aintaining the-grid at a particular setting ofD. C. voltage and'means f o r maintainingl'the conductinglayerl'selective ly at difierent voltages atiesstan but one of which arenegative with respect to the grid voltage and different from the'gridvoltage.

6. In a skew-neck color television cathode ray tube having an electrondirected diagona ly upon a plate adjacent to and across the face of thetube, a transparent conducting layer across the inside of the tube onthe 'plate, a conducting grid extending across the tube' between theelectron gun and the conducting layer adjacent the conducting layer andhaving openings which pass the electron beam toward the conductinglayer, semiconducting phospho'r'of a plurality of different colorsarranged in different areas in the path of the diagonal electron beambetween the grid and the conducting layer beyond the respective openingsin electrical contact with the conducting layer, with the'phosphor of aparticular color in the path of the diagonal beam only at the samedeflection, means for maintaining the grid at a particular setting of D.C. voltage and means for maintaining the conducting layer selectively atdifferent 'D. C. voltages at least all'but one of which are difierentfrom the voltage of the grid.

7. In a color television'cathode ray tube having an electron gundirecting an electron beam diagonally upon'a plate adjacent to andacross the face of the tubefa transparent conducting layer across theinside of the tube on the plate, a conducting grid extending across thetube'between the electron gun and the conducting layer adjacent theconducting layer and having parallel slits which pass'the electron beamtoward the plate, bafiles extending diagonally from one side ofindividual slits toward the conducting layer in the direction of thediagonal beam, a semiconducting layer on each bafiie on the side onwhich the electron beam may impinge on the battle, semiconductingphosphor multipher elements each having a dielectric phosphor layer anda secondary-electron-emitting layer, the thickness of the phosphor layerplus the secondary-electron-emitting layer being between 2 and 20microns, the phosphor layer being of a plurality of different colors,the multiplier elements having phosphor layers of one of the colorsbeing mounted on the semiconducting layers on the bafiles and themultiplier elements having phosphor layers of a plurality of differentcolors being mounted on the conducting layer, the respective multiplierelements being selectively in the path of the electron beam between thegrid and the conducting layer beyond the respective slits with thephosphor of a particular color extending as a strip in the path of thebeam only at the same deflect-ion of the electron beam, means formaintaining the grid at a particular setting of D. C. voltage and meansfor deflecting the diagonal electron beam with respect to the majorplane of the grid to energize difierent phosphor colors.

8. In a color television cathode ray tube having an electron gundirecting a diagonal electron beam upon a plate adjacent to and acrossthe face of the tube, a. transparent conducting layer across the insideof the tube 'on the plate, a conducting grid extending across the tubebetween the electron gun and the conducting layer adjacent theconducting layer and having parallel slits which pass the electron beamtoward the plate, supports between the grid and the conducting layerelectrically connected to the conducting layer, semiconductor phosphorof a plurality of different colors in strips on the conducting layer andin strips on the supports, the phosphor strips on the conducting layerbeing spaced and the phosphor strips on the support being disposedbehind the space between the phosphor strips on the conducting layer,the respective phosphor strips'being selectively in the path of theelectron beam between the grid and the conducting layer beyond therespective shts with the phosphor of a particular color extending as astrip in the path of the beam only at the same deflection of theelectron beam, means for maintaining the grid at a particular setting ofD. C. voltage and means for deflecting the diagonal electron beam withrespect to the major plane of the grid to energize different phosphorcolors.

9. The process of producing color images inside the face plate of acolor television cathode ray tube, which comprises introducing atransparent conducting layer across the inside of the tube adjacent theface plate, distributing phosphor areas over the tube adjacent and inelectrical contact with the conducting layer in a geometrical patternhaving a plurahty of phosphor colors at each locality, projecting anelectron beam in the tube toward the phosphor, screening the beam awayfrom'the phosphor at spaces between individual localities and passingthe beam through to the phosphor at spaces corresponding to individuallocalities, scanning the phosphor of a particular color with theelectron beam, while maintaining a particular voltage relationshipbetween the position of shielding and the conducting layer so that theconducting layer is more negative in potential and shifting the voltagerelationship between the position of shielding and the conducting layerand thereby shifting the scanning beam to encounter another color ofphosphor.

10. The process of producing color image inside the face plate of acolor television cathode ray tube, which comprises introducing atransparent conducting layer across the inside of the tube adjacent theface plate, distributing phosphor areas over the tube adjacent and inelectrical contact with the conducting layer in a geometrical patternhaving a plurality of phosphor colors at each locality, projecting anelectron beam in the tube toward the phosphor, shielding the beam awayfrom the phosphor at spaces between individual localities by applying avoltage difference between the localities and the conducting layer andpassing the beam through to the phosphor at spaces corresponding toindividual localities, scanning the phosphor of a particular color withthe electron beam, while maintaining a particular voltage relationshipbetween the localities of shielding and the conducting layer andrendering the conducting layer more negative in potential with respectto the locality of shielding and thereby deflecting the electron beam toencounter a difierent color of phosphor.

11. The process of producing color images inside the face plate of acolor television cathode ray tube, which comprises introducing atransparent conducting layer across the inside of the tube adjacent theface plate, distributing phosphor areas over the tube adjacent and inelectrical contact with the conducting layer in a geometrical patternhaving a plurahty of phosphor color at each locality, projecting anelec-- tron beam diagonally in the tube on to the phosphor of aparticular color, scanning the phosphor of that color with the electronbeam by 21 applying a potential to the transparentconducting layer anddeflecting the electron beam and scanning the phosphor of a differentcolor.

12. The process of producing color images inside the face plate of acolor television cathode ray tube, which comprises introducing atransparent conducting layer across the inside of the tube adjacent theface plate, distributing phosphor strips over the tube in parallelrelationship adjacent to the conducting layer with a plurality ofphosphor colors at each of a plurality of positions, laterallyseparating the positions from one another to minimize cross reflectionof the electron beam, scanning the successive positions with an electronbeam impinging on the phosphor of a particular color, and deflecting thescanning beam by applying a potential to the transparent coating whichretards the electron beam so that it will encounter phosphor of adifferent color.

13. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof thetube, a transparent conducting layer across the inside of the tubeon the plate, a conducting grid extending across the tube between theelectron gun and the conducting layer, adjacent the conducting layer andhaving slits parallel to one another which pass the electron beam towardthe conducting layer, conducting baflies extending along one side ofindividual slits from the grid and in at least some places supported onthe conducting layer, phosphors of a plurality of different colorsarranged in strips parallel to the slits selectively in the path of theelectron beam on the conducting layer with the phosphors of a particularcolor in the same geometrical relationship to each slit, phosphors of adiiferent color arranged in strips on each baflle in the samegeometrical relationship to each slit, the phosphors of the difierentcolors being selectively in the path of the electron beam through theslits and means for deflecting the electron beam into different angularrelationships to energize phosphors of difierent colors.

14. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof the tube, a transparent conducting layer across the inside of thetube on the plate, a conducting grid extending across the tube betweenthe electron gun and the conducting layer, adjacent the conductinglayer, and having openings which pass the electron beam toward theconducting layer, baffles on one side of the grid openings extendingtoward the conducting layer and limitin deflection of the electron beampassing through the openings, phosphors of a plurality of difierentcolors arranged in different areas in the path of the electron beambeyond the respective grid openings between the grid and the conductinglayer in electrical contact with the conducting layer, with the phosphorof a particular color selectively in the path of the beam only at thesame deflection, means for maintainin the grid at a particular settingof D. C. voltage and means for maintaining the conducting layerselectively at different D. C. voltages at least all but one of whichare different from the voltage of the grid.

15. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof the tube, a transparent conducting layer across the inside of thetube on the plate, a conductin grid extending across the tube betweenthe electron gun and the conducting layer, adjacent the conductinglayer, and having openings which pass the electron beam toward theconducting layer, baflies'on one side of the grid openings extendingtoward the conducting layer and limiting deflection of the electron beampassing through the openings, phosphors of a plurality of difierentcolors arranged in different areas in the path of the electronbeambeyond the respective grid openings between the grid and theconducting layer in electrical contact with the conducting layer, withthe phosphor of a particular color selectively in the path of the beamonly at the same deflection, means for maintaining the grid at aparticular setting of D. C. voltage and means for maintaining theconducting layer selectively at different D. C. voltages at least allbut one of which are diiferent from the voltage of the grid and negativewith respect to the voltage of the grid.

16. In a color television cathode ray tube having an electron gundirecting an electron beam upon a plate adjacent to and across the faceof the tube, a transparent conducting layer across the inside ofthe-tube on the plate, a conductin grid extending across the tubebetween the electron gun and conducting layer, adjacent the conductinglayer, and having openings which pass the electron beam toward theconducting layer, conducting baflles extending from the grid at the sideof individual openings toward the conducting layer, phosphors of aplurality of different colors arranged in different areas selectively inthe path of the electron beam between the grid and the conducting layerbeyond the respective openings distributed on and in electrical contactwith the conducting layer with a phosphor of a particular color in thepath of the beam only at the same deflection, phosphor of a difierentcolor on each baflle, means for maintaining the grid at a particularsetting of D. C. voltage and means for maintaining the conducting layerselectively at diiferent D. C. voltages at least all but one of whichare different from the voltage of the grid.

17. In a color television cathode ray tube having an electron gundirecting a diagonal electron beam upon a plate adjacent to and acrossthe face of the tube, a transparent conducting layer across the insideof the tube on the plate, a conducting grid extending across the tubebetween the electron gun and the conducting layer, adjacent theconducting layer, and having parallel slits which pass the electron beamtoward the plate, supports between the grid and the conducting layer,phosphors of a plurality of diiferent colors in strips on the conductinglayer and in strips on the supports, the respective phosphor stripsbehind each slit being in similar geometrical arrangement, therespective phosphor strips being respectively in the path of theelectron beam between the grid and the conducting layer beyond therespective slits with a phosphor of a particular color extending as astrip in the path of the beam only in the same deflection of theelectron beam, means for maintaining the grid at a particular setting ofD. C. voltage and means for deflecting the diagonal electron beam withrespect to the major plane of the grid to energize different phosphorcolors.

18. A cathode ray tube including an electron gun directing an electronbeam upon a face plate with a partially transparent conducting layer onthe inside of the face plate, coated with strips of luminescentphosphors on the conducting layer, and a conducting grid in closeproximity to the face plate and having two sets of alternating insulatedgrid elements placed between the electron gun and the face plate, meansfor maintaining the respective sets of grid elements at somewhatdifferent D. C. potentials, and means for maintaining the conductinglayer at a plurality of DC. potentials at least all but one of whicharedifierentfrom the respective potentials of the sets of grid elements.

19. A cathode ray tube including a face plate with a partiallytransparent conducting layer on the inside of the face plate, coatedwith strips of luminescent phosphor on the conducting layer, and aconducting grid in close proximity to the face plate and having two setsof alternating insulated grid elements placed between the electron gunand the face plate, means for maintaining the respective sets of gridelements at somewhat difierent D. C. potentials, and means formaintaining the conducting layer at a plurality of D. C. potentials atleast all but one of which are different from the respective potentialsof the sets of grid elements, and negative with respect to thepotentials of the sets of grid elements.

20. In a color television cathode ray tube having an electron gundirecting an electron beam diagonally upon a plate adjacent to andacross the face of the tube, a transparent conducting layer across theinside of the tube on the plate, a conducting grid extending across thetube between the electron gun and the conducting layer, adjacent theconducting layer, and having openings which pass the electron beamtoward the conducting layer, baflies on the conducting grid at one sideof the .grid openings, phosphor strips of a plurality of diiferentcolors in selective paths of the electron beam beyond each slit and atleast one strip being on each bafile, means for maintaining the grid ata particular setting of D. C. voltage and means for maintaining theconducting layer selectively at different D. C. voltages at least allbut one of which are difierent from the voltage of the grid and negativewith respect to the grid.

JENNY BRAMLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,197,625 Teves et al -Apr. 16,1940 2,312,792 Bamford Mar. 2, 1943 2,343,825 Wilson Mar. 7, 19442,446,440 Swedlund Aug. 3, 1948 2,455,710 Szegho Dec. 7, 1948 2,461,515Bronwell Feb. 15, 1949 2,518,200 Sziklai et a1 Aug. 8, 1950 2,529,485Chew Nov. 14,1950 2,530,431 Huffman Nov. 21,1950 2,532,511 OkolicsanyiDec. 5, 1950 2,543,477 Sziklai et al Feb. 27,1951 2,544,690 Koch et alMar. 13, 1951 FOREIGN" PATENTS Number Country Date 866,065 France 1941

